Circuit breakers are well known and commonly used to protect automatic circuit interruption to a monitored circuit when undesired conditions occurs. For example, a circuit breaker is designed to interrupt current flowing in the monitored circuit when it detects one or more of an overload condition, a ground fault condition, or a short-circuit condition.
Typically, a circuit breaker is electrically and physically connected to a load wire via a wire connector, which includes a wire binding screw fastened to a wire connector. The typical wire binding screw is a headless screw (also known as a set screw) that has a shaped drive at one end of the screw for receiving a screwdriver tip. The screwdriver tip is inserted into the drive of the screw to rotate it relative to the wire connector. Depending on the direction of the rotation, a user can fasten or unfasten the load wire to the circuit breaker by rotating the screw.
One problem associated with present headless wire binding screws is that various drive shapes are necessary, based on regional client requirements. For example, circuit breakers sold to Canadian customers generally require a headless wire binding screw with a square-socket drive (also known as a Robertson drive) for receiving a square-shaped screwdriver (also known as a Robertson screwdriver). This requirement is mainly based on the popularity of the Robertson screwdriver in Canada. Furthermore, the Robertson screwdriver is rapidly gaining popularity in the United States.
In contrast, for example, circuit breakers sold to American customers generally require a wire binding screw with a slotted drive for receiving a flatblade screwdriver. This requirement is mainly based on the popularity of the flatblade screwdriver in the United States of America. Accordingly, the same type of circuit breaker may require packaging and/or assembly that either includes various optional headless wire binding screws (e.g., includes both a headless wire binding screw with a Robertson drive and a headless wire binding screw with a slot drive) or that is limited to a specific region (e.g., a circuit breaker having a headless wire binding screw with a Robertson drive is sold only in Canada).
Another type of wire binding screw provided by some manufacturers is a screw with a head that has a slot and Robertson combination drive (also referred to as a headed combination drive screw). The headed combination drive screw is manufactured using conventional cold heading production equipment. The underside of the head allows the equipment to support a screw blank while the combination drive (e.g., slot and Robertson drive) is formed in the screw blank. However, in contrast to the headed screw, a headless screw does not have the underside of the head for providing support to the combination drive when rolling the thread on the screw blank. Slots in slotted headless screws are saw cut after threading. In contrast, in the cold heading process the drive configuration is stamped into the blank before rolling the thread on the screw blank. Accordingly, when the thread is rolled on the screw blank using current manufacturing methods and materials (e.g., cold forming using carbon steel AISI 1010), the combination drive will close up such that the drive tool (e.g., screwdriver) cannot enter the combination drive.
The regional demands for a particular shaped drive in a headless wire binding screw causes inefficiencies related to manufacturing, assembly, and/or marketing of present circuit breakers. For example, based on requirements specific to a particular region, a manufacturer would have to consider expenses associated with two separate circuit breaker assemblies in which the only difference may be the type of the headless wire binding screw that is being provided (e.g., having either a Robertson drive or a flatblade drive).
What is needed, therefore, is a wire binding screw having a slotted-square drive screw for a circuit breaker that addresses the above-stated and other problems.